"It is for us the living, rather, to be dedicated to the unfinished work which they who fought here have thus far so nobly advanced," Lincoln said.

McChrystal noted that less than 1 percent of Americans serve in the military.

"Universal national service should become a new American rite of passage," he says. "At age 18, every young man and woman would receive information on various options for national service."

Aside from serving in the military, young adults could enlist in other areas of national service devoted to urgent issues such as education, healthcare, and poverty, McChrystal says.

"The positions within these branches would be offered through AmeriCorps as well as through certified nonprofits. Service would last at least a year," McChrystal writes.

The positions would have modest salaries to accommodate nonwealthy participants. And "instead of making national service legally mandatory," McChrystal says, "corporations and universities, among other institutions, could be enlisted to make national service socially obligatory."

"Whatever the details of a specific plan, the objective must be a cultural shift that makes service an expected rite of citizenship. Anything less fails Lincoln's test," he adds.